When you might expect the big political story in the United States to be Barack Obama’s first budget, instead commentators this week have been focused on the question of who’s running the Republican party.

It’s quite normal that in a recently defeated party, the most extreme voices come to the fore. Hence the recent prominence of Rush Limbaugh, lunar right talk-radio host. On Sunday Obama’s chief of staff, Rahm Emmanuel, gently stirred the pot by describing Limbaugh as “the intellectual force and energy behind the Republican Party”, and remarking that “whenever a Republican criticizes him, they have to run back and apologize to him, and say they were misunderstood.”

The Republicans responded exactly on cue. Michael Steele, who as chairman of the Republican National Committee has the best claim to be considered the party’s leader, tried to disown Limbaugh:

“Rush Limbaugh, his whole thing is entertainment. Yes, it’s incendiary. Yes, it’s ugly.”

But Limbaugh was having none of this. After he attacked Steele on his radio show, Steele followed Emmanuel’s script by promptly apologising: “I have enormous respect for Rush Limbaugh … There was no attempt on my part to diminish his voice or his leadership.”

On the one hand, this just shows how hard it can be for a long-ruling party dumped into opposition: shorn of its more moderate supporters, it looks inward, tries to consolidate its base, and risks getting caught in a sort of downward spiral of irrelevance.

But it also shows how effective Obama’s tactics have been. By sticking to the high ground and disavowing open partisanship, the administration has given the GOP maximum scope to make trouble for itself. When it comes to attracting moderate voters, running against Limbaugh is like shooting fish in a barrel. As Sean Quinn at fivethirtyeight.com put it, “having already taken control of the public perception of bargaining in good faith, Obama is willing to become more rhetorically aggressive.”

Quinn interprets this as being mostly about winning Republican votes in congress for the administration’s legislative agenda: “Without any Republican willing to stand up to Limbaugh, there’s no middle ground between him and Obama, and nowhere to hide for the few moderate Senate Republicans Obama needs.”

While I’m sure that’s part of the story, I think Obama has a more long-range view. Tarring the Republican party as mad extremists is not just a strategy for this year’s battles in congress; it’s also about discrediting GOP brand for the future and ensuring Democrat supremacy for 2012 and beyond.